Self-change interventions have great potential to aid the many problem drinkers who do not seek formal treatment. Because self-change interventions circumvent some of the barriers associated with traditional treatment services, they may help reduce the harm associated with alcohol abuse among untreated individuals, whose number far exceeds that of the minority who ever access formal alcohol treatment programs. Self-change/self-help materials have the added advantage of being relatively inexpensive, increasing their potential for wide distribution and attendant public health impact. The Internet is one promising route for distributing such materials to a large segment of the population. Three-quarters of Canadians and Americans use the Internet, including a large number who seek health-related information on line. Drinking self-change websites abound on the Internet, but because none has been scientifically evaluated it is unknown whether such sites do more good than harm. By being the first large scale, controlled evaluation, this project intends to advance the science of Internet-mediated intervention as well as provide valuable public health information on the effectiveness of Internet-delivered self-change materials. Specifically, the major objective of this project is to conduct a randomized controlled evaluation of the impact of an Internet-based self-help intervention for problem drinkers in the general population. Participants will be recruited through an ongoing general population survey conducted for the Centre for Addiction and Mental Health (N = 170 after attrition), and will be randomly assigned to be sent a World Wide Web page Internet address and password for the personalized alcohol feedback program or to a no intervention control group. Three and six-month drinking outcomes will be compared between experimental conditions using structural equation modeling. The primary hypothesis is that respondents in the Internet personalized alcohol feedback condition will display significantly improved drinking outcomes at three and six-month follow-ups as compared to respondents in the no intervention control condition. Secondary hypotheses will address the mediating or moderating role of perceived drinking norms, perceived risk and the problem drinker's social reasons for drinking.